The present invention relates to engine control techniques, and more particularly, but not exclusively, relates to gas turbine engine overspeed detection and remediation.
A sudden loss of load for a gas turbine engine can result in a highly destructive failure if not quickly addressed. This type of load loss can occur, for example, when an engine shaft or associated gearing fails. One way to detect if a load loss has occurred is to monitor for an engine overspeed event. One basic type of overspeed detection compares rotational engine speed to a static limit. When this limit is exceeded, an overspeed condition is declared and engine fueling is consequently reduced or shut off. Unfortunately, when the static limit is set too low, false triggering can occur because of brief transient excursions beyond the overspeed limit. Such false triggering typically results in an unwarranted loss of engine power. On the other hand, when the static limit is set to high, the destructive effects of catastrophic, load loss failures are likely to progress further before the overspeed situation is addressed.
One alternative to address these shortcomings is to vary the overspeed limit with a different parameter more closely associated with catastrophic failure load loss, such as rotational acceleration. However, acceleration-based systems are often very sensitive to noise such as might be caused by power transients, electromagnetic interference, lightning, and the like--once again resulting in false triggers and unwarranted engine power loss. Thus, there is a demand for further contributions in this area of technology.